This invention is directed to an improvement in tubular members or pipes, such as used in the drilling and production of oil and gas wells, by the fabrication and use of composite materials in forming the tubular members and is particularly directed to an improvement in tubular members which, when joined together end-to-end, provides a liner-to-liner seal with a single seal ring.
As pointed out in the Related Application, tubular members, such as risers which are connected together end to end in strings, formed of material other than metal, are known to be old, as shown, for example, in the U.S. Pat. No. 3,768,842 to Ahlstone. This patent utilized fiberglass with metallic end pieces to connect one tubular member to another to form the string of pipe.
The use of fiberglass in other tubular members with metallic end connectors is also shown in the U.S. Pat. No. 3,352,557 to Medney. Attention is directed to FIG. 1 herein which is a reproduction of FIG. 2 including the patent reference numerals of that patent where tubes 11a, 13a of fiberglass material are flared at 15a, 17a by rings 35, 37 pressed into the ends of the tubes and attached thereto. Thereafter, metallic outer collar member 43, 45 were brought together and adhered to the flared ends and a threaded slip collar 49 was threaded thereover to form a joint of the union type. In order to form such a union joint, it is apparent that the outer connector rings for each end of the fiberglass tubing and the collar had to be inserted over the fiberglass tubing before the ends of the fiberglass tubing were flared. Typical also of a union joint, the outer diameter of the joint is considerably larger than the diameter of the fiberglass tubing.
The other figures of this patent show different means of connecting the ends together to form the union joint and FIG. 3 shows a gasket 51 at the joint. Reference to the patent itself can be made if more detail is thought necessary. FIG. 2 was selected simply because it was representative of the teachings of the patent and because it showed the threaded coupling 49.
This invention is directed to a composite tubing connector assembly in which a liner of a selected material, such as an elastomeric or thermoplastic material, is formed on a mandrel, then a tube of composite material is formed over the liner with flared ends (upsets) formed at the time of forming the tube. The conventional continuous process of forming the composite tubes may be used. Then, using a split lock ring in conjunction with the upsets, pipe end fittings, such as metal connector box and pins of the type used in the oil and gas industry, may be used as coupling members to form the composite tubing connector assembly. The end fittings may be bonded to the composite tube with a suitable adhesive, if desired. This bonding helps seal the composite tubes in the area of the end fittings and aids in load distribution, if the latter is critical. Too, with such box and pin connectors, only one layer of metal thickness exists radially outwardly of the outer surface of the composite tube as distinguished from the prior art union-type joint.
Utilizing the teachings of this invention, lined composite tubing connector assemblies of one-half to one inch wall thickness and thicker from 20 to 100 feet long are feasible. Also utilizing the teachings of this invention, the lined composite tubing with the upsets may be formed of any suitable length and stored for later connection to standard end fittings of any selected type. The reason for the latter is that the end fittings are not needed to be on the composite tubing at the time of formation, as in the prior art. Also the end fittings may be reused on other composite tubes should the latter malfunction for whatever reason. Whether or not the end fittings are bonded to the composite tubes when possible reuse is contemplated is a matter of choice.